| The rapid development of science and technology has expanded the application of axial flow fan. However the problems it encounters are more diversified, and requires higher performance. The design defects easily lead to reduce efficiency and increase noise of the fan,because of its high speed and complex internal flow. So the optimization design of the internal flow components is helpful to improve its performance. In this paper, a multi-objective optimization mathematical model of the fan is established, and get the impeller,rear guide vanes and other flow components basic design parameters. Basis on the results to study the influence for rear guide vanes blade parameters on the performance of the fan, and get better blade design parameters of rear guide vanes, it more matches the impeller parameters, and effectively improve the fans total pressure efficiency, reduce its power and noise. The main research contents and results are as follows.According to the loss of fan, the objective function of total pressure efficiency and sound pressure level is established respectively. Constraint conditions for the design variables and other parameters are determined appropriately. The optimization model is calculated with multi Island genetic algorithm by combines ISIGHTand Matlab. The initial design model of rear guide vanes, the geometric model of impeller and other components are designed in the SolidWorks software.The influence of axial clearance on the fan performance is analyzed and the reasonable value is determined. From the blade chord, the installation angle at the root of blade, and blade twisting angle to design the airfoil blade of rear guide vanes, with Optimal Latin Hypercube design to obtain the best parameter combination of blade type through the CFD analysis. Comparison of the initial rear guide vanes, the performance of the fan is improve by using the new design rear guide vanes and prove the design is effective. Compared with the original fan, the total pressure efficiency increased by 14%, the shaft power is reduced by 12W. Analysis of internal flow field characteristics of fan shows good liquidity, further proof that the optimum design of the fan is correct.Based on FLUENT noise model the sound power and sound pressure level of the fan is predicted. The simulation results of primary fan is very close to the test results, proving the noise simulation method is correct. The analysis results show that impeller, static vane and the casing at rotating area is the main source of noise. The maximum noise of the new design fan at design speed 18480rpm is 84.3dB, the maximum noise at the original speed 18901rpm is 85.8 dB, that were lower than the original design of fan, prove that the design of each flow components is beneficial to reduce the noise of fan.Strength and dynamic characteristics of the fan impeller is analyzed based on fluid-structure coupling in ANSYS Workbench platform. The analysis results show that the impeller structure stress and deformation are less than the allowable value under different conditions, its strength and stiffness to meet the job requirements. The highest working speed should not exceed 21480rpm within the allowable range of stress. Impeller dynamic characteristics are analyzed through the establishment of the impeller Campbell diagram, it stable operation at design speed. |
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